Parabolic microphone dish at DVinfo.net

Larry Vaughn · February 28th, 2007, 04:14 PM

The responses to Philip's post mention parabolic dishes. A couple weeks ago I thought I needed one to record some bird and alligator sounds. I found a parabolic dish on ebay for hobbyists that wasn't too expensive, about $40 with shipping. It's just a dish meaning that I have to mount an omni mike inside at the focal point about 4" from the surface in this case. A bit crude but smooth inside where it counts.

I'm waiting for the onmi to show up so I don't know how well it will work yet. Also, I picked up a $5.00 clear plastic salad bowl from WalMart that has quite a seashell effect. I'm going to try that too. It's a lot smaller but I couldn't resist it for the price. Plus, I can always put lettuce in it. That might make a good windscreen. Or, maybe shredded cabbage. Any recommendations?

Giroud Francois · February 28th, 2007, 04:42 PM

why not use a satellite dish antenna.
It already has the arm at the focal point and you can find any size for very cheap (even for free).

Andy Tejral · February 28th, 2007, 05:31 PM

Quote:

Originally Posted by Giroud Francois

why not use a satellite dish antenna.

I think that'll work good if your sound source is the same distance as a satellite!

Larry Vaughn · February 28th, 2007, 11:30 PM

You could use a sat dish. But they are not clear, meaning they are harder to aim and they weigh more.

Tim OBrien · March 1st, 2007, 09:22 AM

Psssst...... $10 Wok works too....

Douglas Spotted Eagle · March 1st, 2007, 09:29 AM

So does a very large popcorn-type tupper ware bowl with the bottom drilled out.

Denis Danatzko · March 4th, 2007, 08:55 AM

Douglas Spotted Eagle: I've always wondered if something like that would work, but I've also always been under the impression that placement of the mic was absolutely crucial to getting decent sound, and placement would vary based on the pickup pattern and qualities of the mic being used.

How do you calculate all that? Or don't you? Is listening thru "trial and error" the best way? (Probably the easiest, but is it the best)?

Ty Ford · March 4th, 2007, 09:32 AM

Bounce angles are important and even when you do get that right, the sound is wonky with a dish.

Regards,

Ty Ford

Larry Vaughn · March 4th, 2007, 09:53 AM

I read some info about this at a university web site that deals with ornithology. http://www.birds.cornell.edu/Macaula...bout/1920.html

http://www.telinga.com/index.html click on the white paper link. Could be a bit biased since they sell dishes but it seems like good info.

They say you need a mic placed at the focal point of the parabola. If the reflector isn't a true parabola, you wouldn't get the best results. Sat reflectors are parabolas as are some wire noodle strainers, which work for reflecting wi-fi signals but probably not sound.

Douglas Spotted Eagle · March 4th, 2007, 10:33 AM

Quote:

Originally Posted by Denis Danatzko

Douglas Spotted Eagle: I've always wondered if something like that would work, but I've also always been under the impression that placement of the mic was absolutely crucial to getting decent sound, and placement would vary based on the pickup pattern and qualities of the mic being used.

How do you calculate all that? Or don't you? Is listening thru "trial and error" the best way? (Probably the easiest, but is it the best)?

With a dish...you can never get "good sound." You just can't. But you can practice, and learn the way the setup works whether it's a BigEar or a popcorn bowl.
Same goes for mics that are being used normally. You learn how the mic works, what it's personality is like, and soon, you can use that mic without really thinking too much about placement, because it's a natural part of your workflow. You'll always have small tweaks, but small over a few seconds is better than lots of tweaks while you find the sweet spot.

Jim Michael · March 4th, 2007, 11:24 AM

Many years ago magazines such a Popular Mechanics had articles on building dish mics using a round sled such as http://www.amazon.com/Flexible-Flyer...028820&sr=8-19

A threaded steel rod was used to offset the mic from the center of the sled to the focal point. Not sure if that example above has the right curvature, however the effectiveness of the mic should increase with the radius of the collector.

Paul R Johnson · March 4th, 2007, 11:48 AM

A satellite dish is perfect for this - the idea is that the dish brings the source to a focal point - and you place the microphone capsule at the point and is works. Omnis are usually used as the are directly pressure operated. Cardioids do work, but focus is sometimes a bit tricky. The commment about satellites being a long way away is correct - but all this means is that the focal point is in a slightly different place. Gain wise, the bigger the dish the better. but the bigger dish soon becomes too heavy, and difficult to align properly. Satellite dishs are also often modified spheres - which although good for satellite, don't work as well, audio wise. Overall size also has an impact on frequency response - the bigger, the more bottom end you get - however - most people tend to use a decent graphic or parameteric eq to make them sound more natural. A big dish I had a few years ago, originally from a communicatiosn tower, was 5ft in diameter, and with an omni mic let me here low speaking voices nearly 70 feet away, which was pretty good. If you have access to the dish - give it a shot, the results are quite eerie!

Johan Forssblad · March 29th, 2007, 06:16 AM

Hi,
I bought a parabolic microphone some 22 years ago from a nice man in Sweden, Klas Strandberg. See www.telinga.com
It is made of 1 mm polycarbonate and could be rolled in a bag. He has developed it during many years. If you visit his homepage you can listen to the sound and get great ideas. Many bird watchers are using them.
There are also interesting opinoins like:
If you want to record a bird at 50 meter, should it sound as you are at 50 m or at 1 m distance?
Good luck with your dish.

February 28th, 2007, 04:14 PM	#1
Larry Vaughn Major Player Join Date: Jan 2007 Location: Gainesville, FL Posts: 201	Parabolic microphone dish The responses to Philip's post mention parabolic dishes. A couple weeks ago I thought I needed one to record some bird and alligator sounds. I found a parabolic dish on ebay for hobbyists that wasn't too expensive, about $40 with shipping. It's just a dish meaning that I have to mount an omni mike inside at the focal point about 4" from the surface in this case. A bit crude but smooth inside where it counts. I'm waiting for the onmi to show up so I don't know how well it will work yet. Also, I picked up a $5.00 clear plastic salad bowl from WalMart that has quite a seashell effect. I'm going to try that too. It's a lot smaller but I couldn't resist it for the price. Plus, I can always put lettuce in it. That might make a good windscreen. Or, maybe shredded cabbage. Any recommendations?

February 28th, 2007, 11:30 PM	#4
Larry Vaughn Major Player Join Date: Jan 2007 Location: Gainesville, FL Posts: 201	sat dish You could use a sat dish. But they are not clear, meaning they are harder to aim and they weigh more.

March 1st, 2007, 09:29 AM	#6
Douglas Spotted Eagle VASST Join Date: Jan 2004 Location: Stockton, UT Posts: 5,648	So does a very large popcorn-type tupper ware bowl with the bottom drilled out. __________________ Douglas Spotted Eagle/Spot Author, producer, composer Certified Sony Vegas Trainer http://www.vasst.com

March 4th, 2007, 08:55 AM	#7
Denis Danatzko Major Player Join Date: Mar 2006 Location: NYC Metro area Posts: 579	Homemade Dish: Douglas Spotted Eagle: I've always wondered if something like that would work, but I've also always been under the impression that placement of the mic was absolutely crucial to getting decent sound, and placement would vary based on the pickup pattern and qualities of the mic being used. How do you calculate all that? Or don't you? Is listening thru "trial and error" the best way? (Probably the easiest, but is it the best)? __________________ Denis ------------ Our actions are based on our own experience and knowledge. Thus, no one is ever totally right, nor totally wrong. We simply act from what we "know" to be true, based on that experience and knowledge. Beyond that, we pose questions to others.

March 4th, 2007, 09:32 AM	#8
Ty Ford Inner Circle Join Date: Nov 2004 Location: Baltimore, MD USA Posts: 2,337	Bounce angles are important and even when you do get that right, the sound is wonky with a dish. Regards, Ty Ford __________________ Ty Ford's Audio Bootcamp Field Guide Ty Ford's Audio Video Blog

February 28th, 2007, 04:42 PM	#2
Giroud Francois Inner Circle Join Date: Feb 2004 Location: switzerland Posts: 2,133	why not use a satellite dish antenna. It already has the arm at the focal point and you can find any size for very cheap (even for free).

March 1st, 2007, 09:22 AM	#5
Tim OBrien Regular Crew Join Date: Nov 2006 Location: Palm Beach, Florida USA Posts: 99	Psssst...... $10 Wok works too....

March 4th, 2007, 09:53 AM	#9
Larry Vaughn Major Player Join Date: Jan 2007 Location: Gainesville, FL Posts: 201	focal point I read some info about this at a university web site that deals with ornithology. http://www.birds.cornell.edu/Macaula...bout/1920.html http://www.telinga.com/index.html click on the white paper link. Could be a bit biased since they sell dishes but it seems like good info. They say you need a mic placed at the focal point of the parabola. If the reflector isn't a true parabola, you wouldn't get the best results. Sat reflectors are parabolas as are some wire noodle strainers, which work for reflecting wi-fi signals but probably not sound. Last edited by Larry Vaughn; March 4th, 2007 at 10:16 AM. Reason: add link

March 4th, 2007, 11:24 AM	#11
Jim Michael Major Player Join Date: Dec 2005 Posts: 895	Many years ago magazines such a Popular Mechanics had articles on building dish mics using a round sled such as http://www.amazon.com/Flexible-Flyer...028820&sr=8-19 A threaded steel rod was used to offset the mic from the center of the sled to the focal point. Not sure if that example above has the right curvature, however the effectiveness of the mic should increase with the radius of the collector.

March 4th, 2007, 11:48 AM	#12
Paul R Johnson Inner Circle Join Date: Nov 2005 Location: Lowestoft - UK Posts: 4,045	A satellite dish is perfect for this - the idea is that the dish brings the source to a focal point - and you place the microphone capsule at the point and is works. Omnis are usually used as the are directly pressure operated. Cardioids do work, but focus is sometimes a bit tricky. The commment about satellites being a long way away is correct - but all this means is that the focal point is in a slightly different place. Gain wise, the bigger the dish the better. but the bigger dish soon becomes too heavy, and difficult to align properly. Satellite dishs are also often modified spheres - which although good for satellite, don't work as well, audio wise. Overall size also has an impact on frequency response - the bigger, the more bottom end you get - however - most people tend to use a decent graphic or parameteric eq to make them sound more natural. A big dish I had a few years ago, originally from a communicatiosn tower, was 5ft in diameter, and with an omni mic let me here low speaking voices nearly 70 feet away, which was pretty good. If you have access to the dish - give it a shot, the results are quite eerie!

March 29th, 2007, 06:16 AM	#13
Johan Forssblad Major Player Join Date: Nov 2005 Location: Vittsjö, SKÅNE, SWEDEN Posts: 266	Parabolic microphones Hi, I bought a parabolic microphone some 22 years ago from a nice man in Sweden, Klas Strandberg. See www.telinga.com It is made of 1 mm polycarbonate and could be rolled in a bag. He has developed it during many years. If you visit his homepage you can listen to the sound and get great ideas. Many bird watchers are using them. There are also interesting opinoins like: If you want to record a bird at 50 meter, should it sound as you are at 50 m or at 1 m distance? Good luck with your dish.